The ability to introduce exogenous nucleic acids to cells in the central nervous system (CMS) is a powerful technique with applications in neurobiology research and in treatment of neurological disease. RNA interference (RNAi) is currently the most potent and specific method for blocking gene expression; however, there is not to date a successful in vivo application of RNAi to a mammalian model of neurological disease. The major challenge to realizing the full therapeutic value of RNAi for the CMS lies in the delivery of the nucleic acids to target cells. Synthetic nanoparticles offer in vivo protection, low immunogenicity, and relative ease of manufacturing and scale up, and have been used to deliver plasmid and oligonucleotides to various types of cultured cells. However, successful application of this technology for neuronal cell delivery both in vitro and in vivo has been limited due to low delivery efficiencies. The major goal of this research proposal is to develop nanoparticles that mediate efficient neuronal delivery of short, interfering RNA (siRNA), molecules that mediate RNA interference. We propose to implement a novel strategy to overcome intracellular transport barriers by designing nanoparticles that "hitchhike" on motor proteins that transport vesicles toward the cell body. This goal can be achieved by realizing the following aims: (i) synthesizing nanoparticle formulations that integrate components for neuron targeting, vesicle release, and motor protein-assisted, retrograde transport, and optimizing formulations by evaluating the delivery efficiency in postmitotic neuron-like PC 12 cells, (ii) demonstrating siRNA delivery and specific downregulation of transgene expression in primary neurons, and (iii) achieving nanoparticle delivery to neuronal cell bodies in the brain by retrograde transport from spinal cord injection. Efficient delivery systems for the CNS are crucial for both research and clinical applications; thus, successful completion of this project would result in a major step toward realizing the full potential of this technology. [unreadable] [unreadable]